Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

930
FXUS63 KLOT 301908
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
208 PM CDT Tue Jun 30 2026

.KEY MESSAGES...

- Dangerous heat wave continues into Thursday, with daytimes
  highs in the low to mid 90s and peak afternoon heat indices of
  100 to 105 degrees (locally higher).

- While not a complete wash out, thunderstorm chances increase
  late Thursday, with a couple of waves of showers and
  thunderstorms expected Friday into the 4th of July weekend.
  Some storms may be severe and produce heavy rainfall.

&&

.DISCUSSION...
Issued at 208 PM CDT Tue Jun 30 2026

The ongoing heat and humidity continues to be the primary weather
story through Thursday.

A persistent upper-level ridge, with H5 heights in excess of
596 DAM, will remain centered across Kentucky and Tennessee
through Wednesday, before gradually expanding eastward towards
the central Atlantic coast for the second half of the week.
Strong capping under this ridge will continue curtail the threat
for showers and thunderstorms locally through at least Thursday
afternoon/evening. Accordingly, unabated diurnal heating of the
very moist low-level airmass will push afternoon high
temperatures in the low to mid 90s (highest in the urban areas
around Chicago) each afternoon through at least Thursday. When
combined with surface dewpoints in the low to mid 70s, heat
indices will again top out in the 100-105 degree range (locally
in excess of 105) both Wednesday and Thursday. Meanwhile, expect
very warm overnight temperatures, with readings likely
struggling to fall out of the low 80s in the city tonight and
again Wednesday night. While such readings are not necessarily
uncommon to experience on a day in the middle of summer in our
area, it is less common to experience such conditions on 4+
straight days with little to no relief. It is thus the
cumulative effects of the heat that is most concerning with this
heat, and not necessarily the peak temperatures and heat
indices on an individual day. Therefore, no changes are planned
to going heat headlines currently in effect.

Wednesday, and much of Thursday, waves of severe thunderstorms
will continue to be favored northwest of our area (from the
Plains northeastward through the Upper Midwest) within a belt of
active west-southwesterly upper-level flow residing along the
west-northwestern periphery of the upper-ridge. However, as the
upper ridge begins to expand eastward, it will allow this active
belt of westerly upper-level flow to shift into our area late
in the week. Accordingly, while our area will get relief from
the extreme heat this weekend, it will come at the price of
increasing chances for showers and thunderstorms. While it will
not be raining and storming constantly, it appears we may end up
with a couple of waves of showers and thunderstorms during the
holiday weekend, most notably late Friday and on Saturday. Some
of these storms could be severe and produce torrential
downpours.

KJB

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1230 PM CDT Tue Jun 30 2026

Forecast concerns include...

Gusty southwest winds this afternoon and again Wednesday.
Possible mvfr level clouds Wednesday morning.

A high mvfr/low vfr bkn/ovc deck has developed across northern
IL late this morning and will continue to slowly lift to vfr
shortly, and is then expected to scatter out through the
mid/late afternoon. Another period of mvfr level clouds is
possible Wednesday morning, similar to the past two mornings.
Confidence is low and for now have opted to include scattered
mention for this possibility.

Southwest winds will remain gusty this afternoon but the highest
gusts appear most likely during the mid/late afternoon and then
speeds/gusts will diminish with sunset though periodic gusts
will remain possible for the Chicago terminals tonight. Gusts
will increase back into the lower/mid 20kt range Wednesday
morning. cms

&&

.CLIMATE...
Issued at 1249 AM CDT Tue Jun 30 2026

     .Daily Records for the Upcoming Week........

Chicago (KORD)
            Record High       Record Warm Minimum
June 30       99 (1953)            80 (2018)
July 1       103 (1956)            78 (1931)
July 2        99 (1970)            79 (1911)
July 3       102 (1949)            78 (1911)
July 4       102 (2012)            80 (1921)


Rockford (KRFD)
            Record High       Record Warm Minimum
June 30      102 (1931)            76 (2018)
July 1       101 (1931)            76 (1970)
July 2        99 (1910)            74 (1970)
July 3        99 (1925)            75 (2012)
July 4       102 (2012)            77 (1977)

NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Extreme Heat Warning until midnight CDT Thursday night for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
     ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

IN...Extreme Heat Warning until midnight CDT /1 AM EDT/ Thursday
     night for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 9 PM CDT this evening for Winthrop
     Harbor IL to Gary IN.

&&

$$

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